The novel development described herein relates to a process for coloring substrates, using the application of liquid colorants, in which the assignment of color is done on a pixel-by-pixel basis. Specifically, the following describes a process, and the resulting product, whereby relatively large areas of a substrate may be given the appearance of being uniformly colored by successively replicating or tiling a group of individually colored pixels comprising a repeating unit (i.e., a superpixel) across the substrate surface. The repeating unit is constructed in such a way that if a colorant application error develops, causing one or more pixels within the repeating unit to be colored incorrectly or incompletely, the overall arrangement of the pixels within the repeating unit will render such error less visually apparent when viewed on the substrate.
Many techniques have been developed for patterning or coloring substrates, notably absorbent substrates, and particularly textile substrates. With the development of the electronic computer, such techniques have included the use of individually addressable dye applicators, under computer control, that are capable of dispensing a predetermined, and in some cases, variable, quantity of a dye or liquid colorant to a specifically identified area or pixel on a substrate surface. Such techniques have been disclosed in, for example, commonly-assigned U.S. Pat. Nos. 4,116,626, 5,136,520, 5,142,481, and 5,208,592, the teachings of which are hereby incorporated by reference.
In the devices and techniques described in the above-referenced U.S. patents, the pattern is defined in terms of pixels, and individual colorants, or combinations of colorants, are assigned to each pixel in order to impart the desired color to that corresponding pixel or pixel-sized area on the substrate. The application of such colorants to specific pixels is achieved through the use of hundreds of individual dye applicators, mounted along the length of color bars that are positioned across the path of the moving substrate to be patterned. Each applicator in a given color bar is supplied with colorant from the same colorant reservoir, with different arrays being supplied from different reservoirs, typically containing different colorants. By generating applicator actuation instructions that accommodate the position of the applicator along the length of the color bar and the position of the color bar relative to the position of the target pixel on the moving substrate, any available colorant from any color bar may be applied to any pixel within the pattern area on the substrate, as may be required by the specific pattern being reproduced.
It is contemplated that other arrangements or techniques for systematically applying various colorants to a substrate surface in accordance with pattern data, such as, for example, having one or more sets of colorant applicators that are moved or indexed across the face of a relatively stationary or intermittently indexed substrate, may also employ the teachings herein.
Regardless of the nature or configuration of the patterning device, a common problem with the use of such devices involves the occasional malfunction of one or more of the colorant applicators, as when such applicators become clogged, blocked, mis-aligned, or otherwise become incapable of reliably and accurately dispensing to each assigned pixel the required quantity of the assigned colorant to that pixel. If the malfunction is intermittent, such as an applicator that occasionally dispenses the incorrect quantity of colorant, the resulting patterning irregularity may be relatively unobtrusive, depending, of course, upon the nature of the pattern being reproduced, the nature of the substrate being patterned, and other factors. If the malfunction is persistent, such as an applicator that has become blocked, mis-aligned, or has ceased to function altogether, the resulting patterning irregularity may be so obtrusive as to cause visually objectionable streaks, bands, or the like that tend to extend in the direction of primary relative motion between the colorant applicator(s) and the substrate, hereinafter referred to as the xe2x80x9cmachine directionxe2x80x9d (e.g., as indicated by the arrow in FIGS. 1 and 2).
The result of such malfunctions manifests as linear patterning anomalies known as xe2x80x9cstreaksxe2x80x9d or xe2x80x9cbandsxe2x80x9d and may be somewhat visually analogous to the striations associated with old or worn film or videotape images. Areas of the substrate in which the pattern requires a relatively uniform solid color or shade to be reproduced on the substrate are generally the least tolerant of either type of malfunctionxe2x80x94such malfunctions result in solid color areas that are non-uniform, either due to the formation of the streaks and bands referred to above, or due to otherwise unintended and visually objectionable pattern irregularities. Accordingly, the uniform appearance of such areas patterned by such patterning devices as described above has been particularly dependent upon the absence of colorant applicator malfunctions.
By use of the teachings herein, substrate pattern areas may be generated that effectively emulate uniformly colored pattern areas, but that have dramatically increased tolerance for individual colorant applicator malfunctions that might otherwise render such pattern areas distinctly non-uniform and visually objectionable. In accordance with one embodiment of the teachings herein, areas of the substrate that are intended to carry a solid color or shade instead may be patterned with an arrangement of different colored pixels, selected to replicate the required color on the substrate, that collectively comprise a repeating unit or superpixel.
The distribution of such colored pixels within such superpixel are carefully constructed to avoid or minimize the formation of visually obtrusive clumps or islands of color within the superpixel, as well as the unintended alignment of such pixels either within a given superpixel or across several superpixels, particularly in the machine direction. In single color areas, the former condition tends to promote a speckled or heathered appearance, which may or may not be desirable, while the latter condition tends to generate visually apparent twill lines under some conditions. When such repeating unit or superpixel is tiled or otherwise replicated across the substrate surface and observed at a distance, this patterned areaxe2x80x94although generally comprised of a dense arrangement of chromatically compatible, but not identically colored, pixelsxe2x80x94is capable of serving as an effective visual surrogate for a uniformly colored solid shade area on the substrate.
Advantageously, the resulting pattern area, which may, in some cases, result in a somewhat xe2x80x9cheatheredxe2x80x9d appearance, effectively disguises patterning irregularities due to the misapplication of colorant by individual, improperly functioning colorant applicators in individual pixel areas, particularly in cases in which colorant applicator malfunctions are persistent and result in a systematic patterning irregularity that is replicated throughout the pattern area. It has also been found that, through use of such xe2x80x9cfault-tolerantxe2x80x9d superpixels, the resulting pattern area tends to allow contours in the surface of the substrate, as, for example, would be found in a multi-level carpet substrate, to maintain a desired degree of visual prominence, which the generation of bands, streaks, and the like tends to obscure.
In another embodiment of the teachings herein, the pixels comprising the superpixel may be identically colored, but may be colored in a manner that involves the use of multiple (and technically redundant) colorant applicators to provide an applicator-to-pixel relationship that can disguise individual improperly functioning colorant applicators, as will be discussed in further detail below.
For purposes herein, the following terms shall have the indicated meanings, unless the context or explicit language otherwise dictates.
The term xe2x80x9cpixelxe2x80x9d shall refer to the smallest area or location in a pattern or on a substrate that can be individually assignable or addressable with a given color.
The term xe2x80x9cpatternxe2x80x9d and its derivative terms shall mean assigning or imparting one or more colors to a substrate surface, and shall refer both to the assignment of colors to specific pixels and to the corresponding dispensing of liquid colorants on the substrate surface. When used in the sense of a pattern on a substrate surface, the term shall refer to the arrangement of textile fibers that have been dyed by the application, on a pixel-by-pixel basis, of a liquid colorant to the surface of the substrate. While a pattern typically involves different colors, arranged in pre-determined configurations, placed or to be placed in various areas of the substrate surface, it may also refer to the assignment or generation of a single color in all areas of the substrate surface, i.e., a xe2x80x9csolid colorxe2x80x9d pattern. In either case, the color(s) may be generated on the substrate surface through the pixel-by-pixel application of a single liquid colorant (e.g., if the desired color can be reproduced using a single process color), or the application of several different liquid colorants to form an in situ blend on the substrate surface.
The term xe2x80x9cheatherxe2x80x9d and its derivative terms shall mean small scale chromatic non-uniformities within a patterned area on a substrate, somewhat analogous to grain in a photograph or the halftone structure in a printed halftone image. Substrates with significant heather appear speckled or stippled when viewed at close range, although may appear to exhibit a solid color when viewed at a greater viewing distance. In some cases, the generation of heather is desirable, as it provides for the presentation of a variety of different colors, or different shades of the same color, in a way that is visually apparent, but subtle and unobtrusive.
The term xe2x80x9cadjacentxe2x80x9d and its derivative terms shall be used to mean contiguous, including along a diagonal, i.e., having a shared, common boundary element, including a common side or a common corner.
The term xe2x80x9cside-wise adjacentxe2x80x9d shall refer to a particular kind of adjacent or contiguous orientation in which the common boundary element consists of at least one common side (i.e., the sharing only of a common corner falls within the definition of adjacent, but does not fall within the definition of side-wise adjacent).
The term xe2x80x9cditheringxe2x80x9d shall refer to a computer-generated reconstruction of an image, using only pixels having colors found in a pre-defined xe2x80x9cdither palettexe2x80x9d. Dithering software generates, in pixel-wise fashion, an image in which each pixel is assigned a color from the dither palette that, when the image is viewed from a distance, best approximates the target color at that location within the pattern.
The term xe2x80x9cMulti-pixel Offset Unitxe2x80x9d or xe2x80x9cM.O.U.xe2x80x9d shall be used to describe the smallest group of pixels that collectively represent the desired color. In one embodiment of the teachings herein, an M.O.U. can be thought of as the major component or building block of a superpixel that imparts the correct color (but not necessarily the correct internal placement of pixels) to that superpixel. In that embodiment, several M.O.U.s are arranged so that pixels having the same color are assigned to different columns (i.e., a series of contiguous pixels extending in the machine direction) on the substrate. A specific arrangement of adjacent M.O.U.s can form a superpixel that, when tiled across an area of the substrate, will form the desired color while minimizing the alignment, in the machine direction, of pixels having the same color, thereby making relatively inconspicuous any patterning irregularities (e.g., the formation of streaks and bands) due to the malfunction of any specific colorant applicator.
The term xe2x80x9csuperpixelxe2x80x9d refers to a pre-defined arrangement of pixels, each carrying a pre-determined color (generated by a single process colorant, or by an in situ blend of two or more process colorants applied to the same or adjacent pixels), to be tiled or otherwise replicated across an area on a substrate surface in order to impart a specified color or pattern effect to that substrate surface area. In one embodiment of the teachings herein, a superpixel may be formed by an arrangement of several M.O.U.s or, in another embodiment of the teachings herein, may simply be an arrangement of individual pixels. When used in the context of patterning, the terms xe2x80x9csuperpixelxe2x80x9d and xe2x80x9crepeating unitxe2x80x9d may be used interchangeably. Superpixels can contain several or dozens of individual pixels.
The term xe2x80x9cmachine directionxe2x80x9d shall refer to the relative direction of movement of the colorant applicators as they are dispensing colorant-onto the substrate. It is presumed that the substrate to be patterned is either in the form of a continuous web, e.g., a broadloom floor covering, or is in the form of a series of discrete substrate units, e.g., individual carpet tiles or area rugs, moving along a path leading through the patterning device of choice. Where the applicators are maintained in a fixed position (e.g., on non-moving color bars), the machine direction corresponds to the direction of motion of the substrate through the patterning device. Where the applicators are mounted on a moving platform, e.g., one that traverses across the path of the substrate, the machine direction may be transverse to the direction of motion of the substrate.
The terms xe2x80x9ccolumnxe2x80x9d and xe2x80x9crowxe2x80x9d shall refer, respectively, to axes within pixel arrays extending in the machine direction (column) and transverse to the machine direction (row), respectively. With respect to the patterning device of FIGS. 1 and 2, a column of pixels within an M.O.U. or superpixel extends along the length of the conveyor (and extends vertically in the Figures representing individual pixels).
The term xe2x80x9ctilexe2x80x9d and its derivative terms shall have the conventional mathematical definition, i.e., to position similarly-shaped elements (such as superpixels or other pattern repeat units) having complementary boundaries in adjacent relationship with one another on a surface, so as to cause said complementary boundaries to become common boundaries between adjacent elements, and thereby form a continuous, uninterrupted expanse of said elements over the surface on which said elements are positioned, similar to a jig saw puzzle with identically-shaped pieces.
The term xe2x80x9cprocess colorantxe2x80x9d and its derivative terms shall refer to the colorant applied to the substrate by the colorant applicator system. The term xe2x80x9cprocess colorxe2x80x9d and its derivative terms shall refer to the intrinsic color of the process colorant, prior to any mixing with other colorants on the substrate surface. Process colors, therefore, are colors obtainable without the need for mixing or blending different colorants on the substrate.
The term xe2x80x9ctwill linexe2x80x9d shall refer to the relative position of similarly-colored pixels or pattern elements within a pattern repeat unit that, when the repeat unit is tiled across the substrate, produces an unintended alignment of such pixels or pattern elements that appears as a visually apparent line or band extending, commonly (but not necessarily) in a diagonal direction, over multiple superpixels or pattern repeats.
The term xe2x80x9cin situ blendxe2x80x9d and its derivative terms shall refer to the separate application of two or more colorants to the same or adjacent pixels on a substrate, with at least some mixing or blending of the colorants taking place following such application.
The term xe2x80x9ctarget colorxe2x80x9d shall refer to the color specified in the pattern that is to be reproduced or emulated on the substrate using process colorants, perhaps through the use of in situ blending techniques, dithering techniques, or a combination of those techniques.
The term xe2x80x9cfill colorxe2x80x9d shall refer either to a solid color or shade (i.e., a color or shade that is visually uniform and homogeneous) that is formed by a collection of pixels in which all individual pixels have been assigned the same color, or to a color that is formed by a collection of pixels in which at least two pixels within the collection have been assigned different colors in a manner that minimizes any visually discernable pattern to the positioning of differently colored pixels. In this latter case, the resulting color may exhibit a heather or stipple effect when viewed at close range, but may give the appearance of a solid color when viewed at a distance.
The term xe2x80x9cfill areaxe2x80x9d shall refer to areas within a pattern to which are assigned fill colors.
The term xe2x80x9cperiodicxe2x80x9d and its derivative terms shall refer to the systematic, predictable appearance of an irregularity, a specifically colored pixel, or other identifiable pattern component on the substrate. The term xe2x80x9cnon-periodicxe2x80x9d and its derivative terms shall refer to the random or quasi-random appearance of such pattern components on the substrate.
The term xe2x80x9cpattern artifactxe2x80x9d and its derivative terms shall refer to the introduction of an unintended design element in situations wherein a repeating unit is replicated within an area of the substrate. A pattern artifact arises when certain components within that repeating unit become geometrically aligned with similar components in adjacent repeating units in a way that introduces an unintended design element, such as a twill line, which typically spans many repeating units and is relatively unobtrusive or non-existent when viewed only within the single repeating unit.
The term xe2x80x9cpattern irregularityxe2x80x9d and its derivative terms shall refer to deviations between the pre-determined pattern and the pattern as reproduced on the substrate. A pattern irregularity, if periodic, can form a pattern artifact.
The term xe2x80x9ctextile floor coveringxe2x80x9d shall refer to any absorbent textile substrate (e.g., one that may be described as a non-woven, woven, tufted, bonded, knitted, flocked, or needlepunched textile substrate) that is adapted (perhaps with the addition of an appropriate textile or non-textile backing material) or suitable for placement on a floor or other walking surface. Specifically included as non-limiting examples are carpets, carpet tiles, broadloom rugs, area rugs and mats, any of which may be variously comprised of polyamide fibers, wool fibers, or combinations thereof. Non-limiting examples of carpet tiles are described in more detail in commonly-assigned U.S. Pat. Nos. 4,522,857 and 6,203,881, each hereby incorporated by reference herein.